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About Leukemia
Leukemia is a malignant disease (cancer) of the bone marrow and blood. It is characterized by the uncontrolled accumulation of blood cells. Leukemia is divided into four categories:
myelogenous or lymphocytic, each of which can be acute or chronic. The terms myelogenous or lymphocytic denote the cell type involved. Thus, the four major types of leukemia are:
- Acute Lymphocytic Leukemia
- Chronic Lymphocytic Leukemia
- Acute Myelogenous Leukemia
- Chronic Myelogenous Leukemia
Acute leukemia is a rapidly progressing disease that results in the accumulation of immature, functionless cells in the marrow and blood. The marrow often can no longer produce
enough normal red blood cells, white blood cells and platelets. Anemia, a deficiency of red cells, develops in virtually all leukemia patients. The lack of normal white cells impairs
the body's ability to fight infections. A shortage of platelets results in bruising and easy bleeding.
Chronic leukemia progresses more slowly and allows greater numbers of more mature, functional cells to be made.
New Cases
Among an estimated 30,800 new cases of leukemia in the United States this year, about equal proportions are acute leukemia and chronic types. Most cases occur in older adults;
more than half of all cases occur after age 60. Leukemia usually strikes 10 times as many adults as children. Leukemia is the most common cancer among children and acute lymphocytic
leukemia (ALL) accounts for 80 percent of the childhood leukemia cases.
The most common types of leukemia in adults are acute myelogenous leukemia (AML), with an estimated 10,600 new cases annually, and chronic lymphocytic leukemia (CLL), with some
7,000 new cases each year. Chronic myelogenous leukemia (CML) affects about 4,400 persons each year. Acute lymphocytic leukemia (ALL) will account for about 3,800 cases this year.
Other unclassified forms of leukemia account for the 5,000 remaining cases.
Incidence by Gender
Incidence rates for all types of leukemia are higher among males than among females. In 2002, males are expected to account for more than 57 percent of the cases of leukemia.
(Note: Incidence rates are the number of new cases in a given year not counting the pre-existing cases. The incidence rates are usually presented as a specific number per 100,000
population.)
Incidence by Race and Ethnicity
Incidence rates for all types of cancer are higher among Americans of European descent than among those of African descent. Approximately 130,800 new cancer cases were diagnosed
in 2001 (latest report) among Americans of African descent. The majority of these cases are not blood cancers. African-Americans have an overall cancer incidence rate that is twice
that of American Indians and Hispanics. Minority males have a 50 percent higher rate than minority females across most racial or ethnic groups. These differences are most striking
among older people.
Leukemia is not one of most frequently occurring cancers for minority groups. Leukemia incidence is highest among Caucasian people and lowest among Chinese, Japanese and Korean
people. Leukemia rates are also substantially higher for children of European descent than for children of African descent.
Incidence by Age Group
Incidence rates by age differ for each type of leukemia. The leukemias represented 30 percent of all cancers occurring among children younger than 15 years during 1990-98. In
2002, in the United States, approximately 2,800 children will be diagnosed each year with leukemia including 2,160 with acute lymphocytic leukemia (ALL).
The most common form of leukemia among children under 15 years of age is ALL. About half of the new cases of this disease occur among children. The incidence of ALL among birth
to 4-year-old children is seven and a half times greater than the rate for young adults ages 20 to 24.
There is optimism within centers that specialize in the treatment of children because survival statistics have dramatically improved over the past 30 years. Most children with
ALL are cured. CML, CLL and AML incidence increase dramatically among people who are over the age of 40. They are most prevalent in the sixth, seventh and eighth decades of life.
Signs and Symptoms
Signs of acute leukemia may include easy bruising or bleeding (as a result of platelet deficiency), paleness or easy fatigue (as a result of anemia), recurrent minor infections
or poor healing of minor cuts (as a result of impaired white cell function).
These symptoms and signs are not specific to leukemia and may be caused by other disorders. They do, however, warrant medical evaluation. A proportion of people with chronic leukemia
may not have major symptoms and are diagnosed during a periodic medical examination. The diagnosis of leukemia requires examination of the cells in blood or marrow.
Possible Causes
Anyone can get leukemia. Leukemia affects all ages and sexes. The cause of leukemia is not known. Chronic exposure to benzene in the workplace and exposure to extraordinary doses
of irradiation can be causes of the disease, although neither explains most cases.
Treatment
The aim of treatment is to bring about a complete remission. Complete remission means that there is no evidence of the disease and the patient returns to good health with normal
blood and marrow cells. Relapse indicates a return of the cancer cells and return of other signs and symptoms of the disease. For acute leukemia, a complete remission (no evidence
of disease in the blood or marrow) that lasts five years after treatment often indicates cure. Treatment centers report increasing numbers of patients with leukemia who are in complete
remission at least five years after diagnosis of their disease.
The overall five-year survival rate has tripled in the past 40 years for patients with leukemia. In 1960, the overall five-year survival rate was 14 percent, by the 1970s it had
reached 35 percent, and now the overall five-year survival rate is 46 percent.
During 1992-1998, the relative survival rates were:
- Acute lymphocytic leukemia (ALL): 63.5 percent; 85 percent for children
- Chronic lymphocytic leukemia (CLL): 73 percent
- Acute myelogenous leukemia (AML): 19 percent; 46 percent for children
- Chronic myelogenous leukemia (CML): 34.5 percent
At present, there are approximately 166,359 people are living with leukemia in the United States.
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